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[Bug target/64844] [5 Regression] Vectorization inhibited in gcc5 when loop starts with elem[1], aarch64 perf regression from 4.9.1
- From: "pinskia at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Thu, 29 Jan 2015 02:44:06 +0000
- Subject: [Bug target/64844] [5 Regression] Vectorization inhibited in gcc5 when loop starts with elem[1], aarch64 perf regression from 4.9.1
- Auto-submitted: auto-generated
- References: <bug-64844-4 at http dot gcc dot gnu dot org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64844
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|tree-optimization |target
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
t.c:8:5: note: === vect_update_slp_costs_according_to_vf ===
t.c:8:5: note: cost model: the vector iteration cost = 26 divided by the scalar
iteration cost = 10 is greater or equal to the vectorization factor = 2.
t.c:8:5: note: not vectorized: vectorization not profitable.
t.c:8:5: note: not vectorized: vector version will never be profitable.
t.c:8:5: note: bad operation or unsupported loop bound.
A cost model issue with cortex-a57. The cost model changed in GCC 5 for
cortex-a57. I think this is due to unaligned loads.